The invention relates to a steam generator having a tube bundle with at least one shell side tube support and, more particularly, to a steam generator with a shell side tube support designed for increased fluid flows on the shell side with lower pressure drops, lower vibration and reduced corrosion.
Steam generators employed to generate electric power may circulate water through the shell side of the steam generator over a tube bundle in order to generate steam on the shell side. The tubes in these steam generators may be either U-tubes or straight tubes and must be mechanically supported as a tube bundle by one or more intermediate tube support plates. In early steam generator designs, each tube in a bundle extended through a separate drilled hole in each intermediate tube support plate and the tube bundles were susceptible to corrosion and the deposition of sludge in the region between the tubes and the support plate.
U.S. Pat. No. 4,143,709 to Cunningham discloses a modified steam generator design for use in connection with a pressurized water nuclear plant wherein high temperature, high pressure water is circulated between a reactor vessel and the tube side of a steam generator for generating steam on the shell side. The Cunningham design was developed to reduce the formation of shell side sludge deposits in the regions between the tubes and tube support plates. This particular design differed from the earlier conventional design in that it mechanically supported multiple tubes in the holes in the support plates. Although this design exhibited improved resistance to sludge deposition, it also exhibited a higher than expected pressure drop and a flow stagnation region in the corners formed by the tube support plates where sludge deposition may extend up to about 120.degree. of the tube circumference.
U.S. Pat. No. 4,709,7565 to Wilson discloses a later steam generator design which has been commercially successful. The Wilson design returned to the one hole/one tube approach and in addition broached the support plates to provide flow areas between inwardly extending lands which engage the tubes extending through the holes. This later design provided reduced pressure drops and, at least initially, reduced the flow stagnation regions to no larger than about 40.degree. of the tube circumference. However, experience has indicated that the flow areas along the tubes between the inwardly extending lands may be susceptible to clogging by entrained corrosion particles or sludge.